The storage capacity of an information recording medium (an optical disc) can be increased by increasing the number of layers of an information recording layer. For example, BDXL, which is extended specifications of Blu-ray disc (registered trademark), specifies an optical disc comprising a four-layered information recording layer. However, some types of optical disc have a problem in that the productivity lowers in accordance with an increase of the information recording layer (for example, the manufacturing yield may become poor, the takt time in manufacture may lengthen, etc.). This problem is attributable to the process in which a spiral track groove is molded (transcribed) in each information recording layer.
The problem mentioned above may not occur in a guide-layer-separated optical disc. The guide-layer-separated optical disc comprises a plurality of information recording layers and guide layers provided independently of the information recording layers. (The guide layers are also referred to as servo layers.) In the guide-layer-separated optical discs, the groove mentioned above is formed on the guide layers, but not on the information recording layers. Since the groove is formed on the guide layers, which are smaller in number than the information recording layers, the productivity does not much lower despite an increase in the number of information recording layers.